Methods and arrangements for a mobile communications network

ABSTRACT

The present invention relates to an improved procedure for synchronization of re-configuration of RRC procedures between the radio base station and the UE. This is achieved by associating a new configuration to be used by a UE with an additional UE identity. The UE is normally identified by a first UE identity, but is informed in a re-configuration message that the UE also has the additional UE identity. The UE is identified by the additional UE identity when the new configuration is to be activated. Hence, when the radio base station detects that the UE responds to requests, which included the additional UE identity, the radio base station can conclude that the UE has activated the new configuration.

TECHNICAL FIELD

The present invention relates to methods and arrangements for a mobilecommunications network. In particular, the present invention relates tosynchronization of radio resource control procedures.

BACKGROUND

UTRAN (Universal Terrestrial Radio Access Network) is a term identifyingthe radio access network of a UMTS (Universal Mobile TelecommunicationsSystem), wherein the UTRAN consists of Radio Network Controllers (RNCs)and NodeBs i.e. radio base stations. The NodeBs communicate wirelesslywith mobile user equipments (UEs) and the RNCs control the NodeBs. TheRNCs are further connected to the Core Network (CN). Evolved UTRAN(E-UTRAN) is an evolution of the UTRAN towards a high-data rate,low-latency and packet-optimised radio access network. Further, theE-UTRAN consists of radio base stations (eNBs), and the eNBs areinterconnected and further connected to the Evolved Packet Core network(EPC). E-UTRAN is also being referred to as Long Term Evolution (LTE)and is standardized within the 3^(rd) Generation Partnership Project(3GPP).

The Radio Resource Control Protocol (defined in TS 36.331) is thesignaling protocol responsible for configuring and re-configuring lowerlayers of the UE. These lower layers include the physical layer, MediumAccess Control (MAC), Radio Link Control Protocol (RLC), and Packet DataConvergence Protocol (PDCP). RRC is also responsible for configuring andre-configuring e.g. UE measurements, and the RRC protocol is also incontrol of connected mode mobility. The RRC protocol is terminated inthe eNB and the UE, respectively.

The RRC specification includes several functions and procedures. Onefunction is related to the re-configuration of the UE, as illustrated inFIG. 1.

In this procedure, the eNB in the E-UTRAN issues a reconfigurationmessage transmitted to a UE. Upon successful reception of the messageand in case the reconfiguration procedure is successfully completed, theUE reconfigures the parameters and functions indicated in thereconfiguration message, and responds with a compete-message to the eNB.The reconfiguration message could have a large variety of content,including e.g. L1, MAC, RLC, PDCP or measurement parameters. A handovermay also be commanded with the same message.

In scheduled transmissions on a shared channel, a UE identity of ascheduled transmission must also be conveyed on an out-band controlchannel (HS-SCCH in UTRAN downlink, and PDCCH in E-UTRAN) to identifywhich UE the scheduling command is intended for. In UTRAN and E-UTRANthis identity is not explicitly transmitted, but implicitly included inthe CRC calculation and the HS-SCCH channel coding.

The aforementioned identity must be unique for the UE, in case only asingle UE is scheduled. In UTRAN, this downlink (HS-DSCH) identity iscalled HS-RNTI, while uplink (E-DCH) scheduling is based on an E-RNTI(RNTI—Radio Network Temporary Identity). In LTE, the currentabbreviation for the unique UE identity is C-RNTI, where “C” reflectsthat this UE identity is unique for the UE in this cell. An UE may obeyscheduling commands associated with several such identities.

In LTE, scheduling is the responsibility of the eNB—both in the uplinkand the downlink:

-   -   In the downlink (DL), information on the PDCCH is sent in        parallel with the data on the DL-SCH, such that the right UE can        decode the data correctly.    -   In the uplink (UL), information on the PDCCH is sent prior to        the event when the UE should send its data on UL-SCH, such that        the UE can encode and transmit the data correctly.

To successfully receive the aforementioned data, it is important thatthe two peers (UE and eNB) have compatible configurations.

In the communication between the UE and the eNB, it is often criticalthat the two peers have compatible configurations, i.e. that thetransmitter and receiver uses compatible ways of communicating on allprotocol levels. Therefore, it is important or at least desirable thatthe UE and eNB takes the new reconfiguration into use at the same time.

It should be noted that the aforementioned RRC reconfiguration messageis transmitted over the air interface that is subject to strongvariations in link quality such as fast and slow fading resulting intransmission errors. Therefore, the reconfiguration message can be lostor delayed by re-transmissions by lower layer protocols. LTE RLCsupports ARQ (automatic repeat request) and LTE MAC supports Hybrid ARQto recover from such transmission errors.

Thus, it may be difficult for the eNB to exactly know when the UE hastaken a new configuration into use. It should also be noted that ARQ andHARQ feedback is subject to transmission errors, why such indicationsonly give a hint of when the UE may have successfully received the RRCconnection re-configuration message. Uncertainty of the required UEprocessing time to complete the reconfiguration procedures indicated inthe message will further add to the uncertainty of when the UE isprepared to switch from one configuration to another. This timinguncertainty of when the reconfiguration is competed is illustrated witha dashed box in FIG. 1.

In a particular example, the case when the eNB issues a Layer 1 MIMOreconfiguration is considered, where a UE is currently configured toreceive the Physical Downlink Shared Channel (PDSCH) with e.g. transmitdiversity, but the desire is to reconfigure PDSCH to spatialmultiplexing. Clearly, a UE configured to one of a set of available MIMOschemes will not be able to receive PDSCH if the transmitter (eNB) isusing a different scheme. Thus, if the reconfiguration of the PDSCH isasynchronous, there is a risk that the connectivity between the UE andthe eNB is lost.

Consider e.g. the case where a HARQ feedback error occurs during thetransmission of the DL RRC CONNECTION RECONFIGURATION message containinga critical L1 reconfiguration. A HARQ feedback error denotes the casewhen the HARQ transmitter misinterprets the feedback received from thereceiver.

Assume that a negative acknowledgement (NACK) was interpreted as apositive acknowledgement (ACK) by the eNB. We refer to this error as anNACK-to-ACK error.

In this case, eNB will assume that the UE has successfully received thereconfiguration message and will take the new configuration into usewithin, say, 10 ms after the reception of the falsely decoded ACK.However, as the eNB then switches to the new configuration, the UE willnot be able to receive any data on the reconfigured PDSCH, as the UE didnot receive the reconfiguration message. Similarly, the eNB may lackmeans to receive any UL transmissions in case the reconfigurationincluded a critical reconfiguration of uplink L1 parameters.

In UTRAN (TS RRC 25.331), the present synchronization problem is solvedby an “activation time” (a reference to a certain Connection FrameNumber, CFN) that can be included in an RRC message in order to assurethat the UE starts using a new configuration exactly at the same timeinstance as the Node B. This referenced CFN should occur sufficientlyfar in the future, such that the configuration message can be receivedby the UE, and the UE has time to issue the required reconfigurations.In a successful operation, the UE and Node B then switch exactly at thesame moment to the reconfigured configuration.

Since the RRC message may be subject to radio link control (RLC)retransmissions the activation time must be set far enough into thefuture to allow for retransmissions of the message. Even if the averageretransmission delay is small there are a few percent of the messagesthat needs several retransmissions. The activation time needs to be setto cover also the worst case which leads to that synchronizedre-configuration in UTRAN causes a relatively long delay. This affectsthe signalling performance.

Thus, there is a need to provide a solution for synchronousreconfigurations in LTE without an activation time, by which theambiguity with regards to the current configuration in the UE preferablycan be avoided.

SUMMARY

Thus the objective problem of the present invention is to provide animproved procedure for synchronization between the radio base stationand the UE of re-configuration of RRC procedures.

This is achieved by associating a new configuration to be used by a UEwith an additional UE identity. The UE is normally identified by a firstUE identity, but is informed in a re-configuration message that the UEalso has the additional UE identity. The UE is identified by theadditional UE identity when the new configuration is to be activated.Hence, when the radio base station detects that the UE responds torequests, which included the additional UE identity, the radio basestation can conclude that the UE has activated the new configuration.

According to a first aspect of the present invention, a method in aradio base station for activating a radio resource reconfiguration in aUE and in the radio base station is provided such that the radio basestation can conclude when the UE is ready to start the newconfiguration. The UE being subject to the reconfiguration isidentifiable by a first UE identity. In the method, a reconfigurationmessage is sent indicating a new configuration to be used by said UE andthe reconfiguration message comprises a second UE identity for said UE.The second UE identity is associated with said new configuration. Thenew configuration is activated and an indication that the UE isidentifiable by the second UE identity is received. When the indicationthat the UE is identifiable by the second UE identity is received, theUE is ready to start transmission or reception with the newconfiguration.

According to a second aspect of the present invention a method in a UEfor activating a radio resource reconfiguration in a UE and in a radiobase station is provided such that the radio base station can concludewhen the UE is ready to start the new configuration. The UE beingsubject to the reconfiguration is identifiable by a first UE identity.In the method, a reconfiguration message is received indicating a newconfiguration to be used by said UE. The reconfiguration messagecomprises a second UE identity for said UE and the second UE identity isassociated with said new configuration. The UE activates the newconfiguration and indicates to the radio base station that the UE isidentifiable by the second UE identity.

According to a third aspect of the present invention a radio basestation for activating a radio resource reconfiguration in a UE and inthe radio base station is provided such that the radio base station canconclude when the UE is ready to start the new configuration. The UEbeing subject to the reconfiguration is identifiable by a first UEidentity. The radio base station comprises a transmitter for sending areconfiguration message indicating a new configuration to be used bysaid UE, wherein the reconfiguration message comprises a second UEidentity for said UE and the second UE identity is associated with saidnew configuration, a processing unit for activating the newconfiguration, a processing unit for activating the new configuration, areceiver for receiving an indication that the UE is identifiable by thesecond UE identity and a processing unit for concluding that the UE isready to start transmission or reception with the new configuration whenthe indication that the UE is identifiable by the second UE identity isreceived.

According to a fourth aspect of the present invention a UE foractivating a radio resource reconfiguration in a UE and in a radio basestation is provided such that the radio base station can conclude whenthe UE is ready to start the new configuration. The UE being subject tothe reconfiguration is identifiable by a first UE identity. Further, theUE comprises a receiver for receiving a reconfiguration messageindicating a new configuration to be used by said UE, wherein thereconfiguration message comprises a second UE identity for said UE andthe second UE identity is associated with said new configuration. The UEcomprises further a processing unit for activating the newconfiguration, and a transmitter for indicating to the radio basestation that the UE is identifiable by the second UE identity.

An advantage with embodiments of the present invention is that a networkcan start a new configuration with a reduced delay since there is noneed for an activation time to synchronize the reconfiguration, suchthat the new configuration is taken into use simultaneously in both theUE and the radio base station. In particular, with the embodiments ofthe present invention, it is possible to activate the new configurationas soon as the reconfiguration message has been received and processedby the UE, as opposed to the solution with an activation time, where theactivation time must be configured to a value larger than the worst-casedelay of the transmission of the reconfiguration message as well aslongest possible reconfiguration delay in the UE. With a too shortactivation delay, it could happen that the radio base station would takethe new configuration into use before the UE is ready, potentiallyresulting in a lost connection. Thus, with embodiments of the presentinvention, the average reconfiguration delay is reduced compared to theuse of activation times. Furthermore, the solution according toembodiments of the present invention is also more robust, as there is norisk of connection loss due to too aggressive activation time values.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an RRC re-configuration procedure according to priorart.

FIG. 2 illustrates a re-configuration procedure according to oneembodiment of the present invention.

FIG. 3 illustrates a re-configuration procedure according to anotherembodiment of the present invention.

FIGS. 4 and 5 illustrate flowcharts of methods according to embodimentsof the present invention.

FIG. 6 shows schematically the UE and the radio base station accordingto embodiments of the present invention.

DETAILED DESCRIPTION

The present invention will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. The invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. In thedrawings, like reference signs refer to like elements.

Moreover, those skilled in the art will appreciate that the means andfunctions explained herein below may be implemented using softwarefunctioning in conjunction with a programmed microprocessor or generalpurpose computer, and/or using an application specific integratedcircuit (ASIC). It will also be appreciated that while the currentinvention is primarily described in the form of methods and devices, theinvention may also be embodied in a computer program product as well asa system comprising a computer processor and a memory coupled to theprocessor, wherein the memory is encoded with one or more programs thatmay perform the functions disclosed herein.

Accordingly, the present invention provides a user equipment (UE), aradio base station (RBS) and methods thereof for synchronizingactivation, of a new configuration between the UE and the eNB. By usingthe methods and arrangements of the present invention, the eNB candetermine when the UE is ready to use the new configuration. This isachieved by associating a new configuration to be used by the UE with asecond UE identity. The UE is normally identified by a first UEidentity, but is informed in a re-configuration message that the UE alsohas the second UE identity. The UE is identified by the second UEidentity when the new configuration is to be activated. Hence, when theradio base station detects that the UE is identifiable by the second UEidentity, the radio base station can conclude that the UE has activatedthe new configuration. By using the present invention, it is possiblefor the eNB to deduce if the UE has successfully taken the newconfiguration into use, regardless of the aforementioned uncertaintiesin the transmission of the reconfiguration message.

Note that the original configuration will be denoted by “oldconfiguration” and the re-configured configuration by the “newconfiguration”.

An embodiment of the present invention will now be described in thecontext of an LTE network. However, as a person skilled in the artrealizes, the embodiments are not limited to LTE but can be applied toother wireless communications networks.

Turning now to FIG. 2, illustrating a radio base station (eNB) and a UEof an LTE network. The eNB is connected to an Evolved Packet Core (EPC)network. Moreover, the UE is identified by a first Radio NetworkTemporary Identifier (RNTI), exemplified by a C-RNTI, which is a uniqueidentity of the UE in the cell. In a first step 201, the eNB sends a RRCconnection re-configuration message to the UE. The RRC connectionre-configuration message comprises an Indication of the newreconfiguration and a second C-RNTI associated with the newconfiguration, wherein the second C-RNTI identifies the UE inconjunction with the new configuration.

In a second step 202, the UE may send HARQ feedback to acknowledge thereconfiguration message before the RRC reconfiguration procedure in theUE is finalized. The new configuration is now activated 203 in the UEand the eNB schedules 204 the UE by using the second C-RNTI and maythereby activate the new configuration. Then, the UE sends a RRCreconfiguration complete message 206. The RRC configuration completemessage is in this example sent on the new configuration. It shouldhowever be noted that the RRC reconfiguration complete message could besent either before or after the actual reconfiguration. This does notpreclude that some other data is sent in parallel or just before the RRCconfiguration complete message. If sent after reconfiguration, the RRCconfiguration complete message will be one of the first pieces of datathat is sent on the new configuration.

Alternatively, the UE may take the reconfiguration into use apre-defined time (milliseconds) or subframes after the successfulreception or HARQ acknowledgement of the reconfiguration message. Thisis to ensure that the UE has time to process the content of thereconfiguration message and to ensure that eNB may receive feedback onthe reception status in the UE.

As noted, the HARQ feedback may be subject to reception errors, why theeNB provides mechanisms to recover from any misalignment between theanticipated status in the UE and the true status in the UE with regardsto the successful reception of the configuration message and thesuccessful completion of the reconfiguration procedure in the UE. Therecovery includes the following eNB embodiments:

-   1. NACK-to-ACK error—The reconfiguration message was not received by    the UE: The eNB detects that the UE does not respond to scheduling    on the “new” C-RNTI, and may recover the connection to the UE by    scheduling the UE on the “old” C-RNTI.-   2. ACK-to-NACK error—The eNB assumes that the UE still uses the old    configuration, but the UE has taken the new configuration into use.    In case the UE does not respond on the “old” C-RNTI, the connection    to the UE may be restored by the eNB by scheduling the UE on the    “new” C-RNTI.

In case the UE received the reconfiguration message but the message isrejected by the UE, then the UE should request for uplink resourcesusing the “old” C-RNTI according to already agreed procedures.

As stated above, in step 204, the eNB sends a scheduling command to theUE wherein the UE is identified by at least the second RNTI. Then thenew configuration is activated 205 by the eNB such that it can receive aresponse to the scheduling command with the new C-RNTI. When the UE instep 207 obeys to this scheduling command, the eNB can conclude that theUE has activated the new configuration since it responds to the secondRNTI which is associated with the new configuration and transmissionwith the new configuration can start 208. The eNB may schedule the UEusing both RNTIs, but the eNB knows that the reconfiguration wassuccessful only when the UE responds on the new RNTI. If both RNTIs areused, the UE may respond to one RNTI at a time. If the UE is configuredto use one RNTI at a time, the UE will stop responding to any commandsassociated with the first RNTI when the second RNTI and associatedconfiguration is taken into use. If the UE does not respond to thescheduling command, then the eNB can try to recover the UE by schedulingwith the “old” RNTI, in which case the eNB should again use the oldconfiguration. The need to recover could occur e.g. in the case of aNACK-to-ACK error, as described above.

The approach with multiple C-RNTIs assigned to the same UE, wherein eachC-RNTI is associated with a specific configuration outlined aboveprovides means to synchronize the LIE re-configuration with the eNB suchthat the eNB can unambiguously deduce which configuration the UE iscurrently using. The same result can also be achieved with a UE thatuses one RNTI at a time, where the UE abandons the first RNTI when thesecond RNTI is taken into use.

Another way to reduce the timing uncertainty of when the UE takes thenew configuration into use is illustrated by further embodiments of thepresent invention. These embodiments introduce the mechanism ofcommanding the UE to perform a UE initiated procedure such as a RandomAccess procedure in association with the reconfiguration message priorto taking the new configuration into use as illustrated in FIG. 3. I.e.,the eNB sends in step 301 a RRC reconfiguration message comprising thenew configuration, a second UE identity such as a second C-RNTIassociated with the new configuration and a request to the UE to performa UE initiated procedure using the second C-RNTI). If the UE decodes theRRC reconfiguration message correctly, the UE activates in step 302 thenew configuration and sends in step 303 layer 2 acknowledgement. Inresponse to the request to perform a UE initiated procedure, the UEinitiates the UE initiated procedure in step 305 using the secondC-RNTI. When the eNB in step 306 detects that the UE has initiated therequested UE initiated procedure, the eNB can conclude that the UE isready to use the new configuration. During, or preferably after thedetection of the UE initiated procedure, the eNB activates 304 the newconfiguration. (In general, the UE initiated procedure, e.g. the RACHprocedure, is independent of the actual reconfiguration that isassociated with the RNTI. I.e. the eNB only needs to be prepared toreceive the RA attempt by the UE.) Using the new configuration, the UEsends 307 a layer 3 (RRC reconfiguration complete message)acknowledgement. It should however be noted that the RRC reconfigurationcomplete message could be sent either before or after the actualreconfiguration. Then, transmission with the new configuration betweenthe UE and the eNB can start as illustrated by step 308.

With this approach, the eNB can assume that the UE uses the newconfiguration when it detects that the UE has initiated the UE initiatedprocedure. I.e., when the UE initiated procedure is a random accessprocedure the eNB detects that the UE has initiated (and in this casealso completed) the UE initiated procedure when the UE appears on theRandom Access Channel (RACH).

The eNB may allocate a contention free resource for the RA attempt. Inaccordance with the present invention, the new configuration isassociated with the second UE identity (e.g. the second C-RNTI), suchthat the RA procedure resulting from the command in the reconfigurationmessage can be distinguished from any other random access attemptsinitiated by a UE or the eNB.

Furthermore, the UE may be configured to be scheduled on multiple UEidentities (e.g. C-RNTIs), wherein each of the multiple UE identities isassociated with a configuration. Accordingly, the UE may be configuredto obey the commands following the configurations associated with eachof the UE identities. In addition, the eNB may also configure orre-configure multiple UE configurations to the UE, where each of theconfigurations is associated with a unique UE identity.

In this case, multiple identities may be configured to the UE, each ofwhich is associated with a separate identity. In such a case oneconfiguration may be used while reconfiguring the other. Further, it ispossible to switch between the different configurations by simplyassigning grants using the available RNTIs.

As illustrated in the flowcharts of FIGS. 4 and 5, embodiments of thepresent invention relate to a method in the UE and to a method in theeNB. The methods concern activation of radio resource reconfigurationsin a UE and in a radio base station, wherein the UE being subject to thereconfiguration is identifiable by a first UE identity. By using themethods the eNB can determine when the UE is ready to use the newconfiguration.

The method in the radio base station is illustrated in FIG. 4 andcomprises the steps of:

-   401. Send a reconfiguration message indicating a new configuration    to be used by said UE, wherein the reconfiguration message comprises    a second UE identity for said UE and the second UE identity is    associated with said new configuration.-   402. Activate the new configuration.-   403. Receive an indication that the UE is identifiable by the second    UE identity. Note that step 403 may be performed prior to 402 in    some embodiments of the present invention.-   404. Conclude that the Ue is ready to start transmission or    reception with the new configuration when the indication that the UE    is identifiable by the second UE identity is received.

According to one embodiment, step 402 comprises the further steps of:

-   403 a. Send a scheduling command to said UE by using at least the    second UE identity.-   403 b. Receive a response to the scheduling command with the second    UE identity.

According to a further embodiment, the reconfiguration message comprisesa request to the UE to perform a UE initiated procedure in associationwith the reconfiguration, and the step 403 comprises the step ofdetecting 403 c an indication that the UE initiated procedure isinitiated.

The method in the UE is illustrated in FIG. 5 and comprises the stepsof:

-   501. Receive a reconfiguration message indicating a new    configuration to be used by said UE, wherein the reconfiguration    message comprises a second UE identity for said UE and the second UE    identity is associated with said new configuration.-   502. Activate the new configuration.-   503. Indicate to the radio base station that the UE is identifiable    by the second UE identity.

According to an embodiment of the present invention, the step 503comprises the steps of

-   503 a. Receive a scheduling command, wherein the UE is identified by    the at least the second UE identity.-   503 b. Send a response to the scheduling command.

According to a further embodiment, the reconfiguration message comprisesa request to the UE to perform a UE initiated procedure in associationwith the reconfiguration, and the step 503 comprises the step ofinitiate 503 c the UE initiated procedure in association with thereconfiguration.

Accordingly, embodiments of the present invention relates to a radiobase station 601 (e.g. an eNB) and to a UE 600 as illustrated in FIG. 6.The UE being subject to the reconfiguration is identifiable by a firstUE identity. The radio base station comprises a transmitter 602 forsending a reconfiguration message indicating a new configuration to beused by said UE, wherein the reconfiguration message comprises a secondUE identity for said UE and the second UE identity is associated withsaid new configuration. The radio base station comprises further aprocessing unit 604 for activating the new configuration. The UEcomprises a receiver 605 for receiving the reconfiguration message.Moreover, the UE comprises a processing unit 606 for activating the newconfiguration, and a transmitter 607 for indicating to the radio basestation that the UE is identifiable by the second UE identity since ithas activated the new configuration. Hence, the radio base stationcomprises further a receiver 603 for receiving an indication that the UEis identifiable by the second UE identity and the processing unit 604for determining that the UE is ready to use the new configuration whenthe indication that the UE is identifiable by the second UE identity isreceived.

The transmitter 602 of the radio base station is further configured tosend a scheduling command to said UE by using at least the second UEidentity and the receiver of the UE is further configured to receive thescheduling command. The receiver 603 of the radio base station is henceconfigured to receive a response to the scheduling command with thesecond UE identity and the transmitter 602 of the UE is configured tosend a response to the scheduling command, accordingly.

The transmitter 602 of the radio base station is further configured tosend the scheduling command to the UE by using at least the second UEidentity e.g. when an acknowledgement to the reconfiguration message isreceived at the radio base station from the UE.

According to one embodiment, the reconfiguration comprises a request tothe UE to perform a UE initiated procedure in association with thereconfiguration. In this case the processing unit 606 of the UE isconfigured to initiate the UE initiated procedure in association withthe reconfiguration and the receiver 603 of the radio base station isconfigured to detect that the UE initiated procedure is initiated.

The present invention is not limited to the above-described preferredembodiments. Various alternatives, modifications and equivalents may beused. Therefore, the above embodiments should not be taken as limitingthe scope of the invention, which is defined by the appending

The invention claimed is:
 1. A method in a radio base station foractivating a radio resource reconfiguration in a User Equipment (UE) andin the radio base station, wherein the UE being subject to thereconfiguration is identifiable by a first UE identity, and wherein themethod comprises: sending a reconfiguration message indicating a newconfiguration to be used by said UE, wherein the reconfiguration messagecomprises a second UE identity for said UE and the second UE identity isassociated with said new configuration; activating the newconfiguration; receiving an indication that the UE is identifiable bythe second UE identity; and determining that the UE is ready to starttransmission or reception with the new configuration when the indicationthat the UE is identifiable by the second UE identity is received;wherein the first UE identity is a first Radio Network TemporaryIdentifier (RNTI); wherein the second UE identity is a second RNTI; andwherein the receiving an indication comprises: sending a schedulingcommand to the UE by using at least the second UE identity after apredetermined time period has elapsed after receiving an acknowledgementto the reconfiguration message at the radio base station from the UE;and receiving a response to the scheduling command with the second UEidentity.
 2. The method according to claim 1, wherein thereconfiguration is sent in a radio resource control protocol message. 3.A radio base station for activating a radio resource reconfiguration ina User Equipment (UE) and in the radio base station, wherein the UEbeing subject to the reconfiguration is identifiable by a first UEidentity, said radio base station comprising: a transmitter for sendinga reconfiguration message indicating a new configuration to be used bysaid UE, wherein the reconfiguration message comprises a second UEidentity for said UE and the second UE identity is associated with saidnew configuration; a processing unit for activating the newconfiguration; a receiver for receiving an indication that the UE isidentifiable by the second UE identity; and a processing unit fordetermining that the UE is ready to start transmission or reception withthe new configuration when the indication that the UE is identifiable bythe second UE identity is received; wherein the first UE identity is afirst Radio Network Temporary Identifier (RNTI); wherein the second UEidentity is a second RNTI; wherein the transmitter is further configuredto send a scheduling command to said UE by using at least the second UEidentity after a predetermined time period has elapsed after anacknowledgement to the reconfiguration message is received at the radiobase station from the UE; and wherein the receiver is further configuredto receive a response to the scheduling command with the second UEidentity.
 4. The radio base station according to claim 3, wherein thereconfiguration is sent in a radio resource control protocol message.